Dam construction and repair



O f- 8, 1940- B. C.-COLLIER DAM CONSTRUCTION AND REPAIR Filed Sept. 2, 1959 INVENTOR BRYAN C C01 (/51? w'k m ,5 ATTORNEY Patented Oct. 8, 1940 UNITED STATES OFFICE DAM CONSTRUCTION AND REPAIR Bryan G. Collier, Allentown, Pa.,

assignor to Cement Gun Company, a company of Delaware Application September 2, 1939, Serial No. 293,175

4 Claims.

The present invention relates to concrete dam construction and more particularly to a concrete dam having a drainage system on its downstream face covered by a facing of suitable material, such as Gunite, either where such systems were installed in connection with the repair of the dam or in connection with the original construction thereof.

The surfaces of concrete'structures often, under the conditions to which they are subjected, deteriorate and pieces of the concrete break away, thereby leaving surfaces which deteriorate much more readily than the original surfaces. Deterioration of such surfaces results from many causes, for example seepage of water through the concrete of a wall or dam and more particularly such seepage in connection with freezing. Surfaces of concrete structures which have become damaged due to such deterioration cannot be satisfactorily repaired by the use of concrete but may be by the use of Gunite which is formed by a mixture of cement and sand blown from a cement gun through a hose to a nozzle, where water is added in just sufficient quantity to hydrate the mixture, and then is blown against a suitable form or backing in a dense layer. When thoroughly set, the Gunite is substantially waterproof. In repairing the face of a concrete dam where there is no substantial seepage, entirely satisfactory results may be attained by merely covering the surface of the dam with a suitable layer or facing of Gunite. However, if there be seepage of a substantial amount of water through the concrete of a dam, water would collect back of the Gunite facing and might eventually cause cracking of the Gunite due to freezing or even to hydrostatic pressure. At more-or-less frequent intervals, particularly at points where seepage of water through the concrete is substantial, weep pipes may be installed in the concrete and, in the event that a Gunite facing be applied to the downstream side of the dam, these weep pipes would extend through said Gunite facing. This arrangement would prevent the collection of water behind the facing at such wet spots but, as has been found in practice, does not provide sufficient protection against the accumulation of water back of the water-resisting facing or blanket of Gunite. As a matter of fact, even where the downstream of the concrete appears to be dry, it is not safe to assume that there is no seepage through the concrete of water which would collect back of such a facing and tend to cause destruction thereof. For example, some along these joints.

parts of the exposed concrete may give theimpression of no seepage, in that the seepage water may be evaporated substantially as soon as it appears at the exposed concrete surface, but such evaporation might be prevented by'the application of a Gunite facing thus causing the objectionable collection of the seepage water back of the facing.

An object of the present invention is to provide a concrete dam with a facing of Gunite or the like in such a manner as to avoid any cracking of the facing due to collection of water back of the same. Another objection of the invention is to provide an improved method of repairing the downstream faces of concrete dams. A further object is to provide a concrete dam having a facing of dense cementitious material and a drainage system between the facing and the concrete adapted to carry off substantially all of the water seeping through the concrete, and thereby prevent cracking of the facing which might otherwise occur due to freezing of the water or to hydrostatic pressure. According to one way of carrying out the present invention, the downstream face of the concrete dam is first provided with a suitable drainage system adapted to drain substantially the entire surface thereof. To this end the dam may be provided at said downstream face with substantially parallel main drainage troughs extending downwardly from the upper part of the wall.

At the sides of the main troughs, there may be provided branch troughs inclined toward the main troughs into which they discharge and arranged to drain substantially the entire downstream face of the. concrete. Where the dam has upright construction or expansion joints, certain of the main troughs may conveniently be formed In connection with the repair work, loose material is removed as by chipping, from the downstream face of the dam, and the main and branch troughs may be formed in any suitable manner as by chipping.

After all these troughs have been formed, the troughs may be covered with plates of suitable material, such as Elastite, to serve as a backing against which the Gunite may be shot. After the backing plates are in position over the troughs, thus forming enclosed ducts, there may be placed over the plates covering the main troughs expansion joints or strips of suitable material, such as copper. Then, after placing reenforcing mesh over the entire surface except at the expansion strips, the Gunite is blown into place to cover the mesh and form a layer of substantially surficient thickness, except over the expansion strips where grooves may be provided at the outer face of the Gunite layer.

Other objects, features and advantages will appear upon consideration of the following detailed description and of the drawing in which:

Fig. 1 is an elevation of the downstream face of a dam showing substantially parallel main drainage troughs extending downwardly to carry off seepage water and branch troughs in panels between the main troughs to drain into the main 'troughs at the sides of the panels, and showing a panel in which the troughs have been covered with Gunite and an adjacent panel before the application of the Gunite.

Fig. 2 is a vertical section on Fig. 2;

Fig. 3 is a section on the line'33 of Fig. 1; and

Fig. 4 is a section on the line 4-4 of Fig. 1.

Referring to the drawing, there is illustrated a dam l comprising a concrete body H and a facing I2 of any suitable material such as gunite. As illustrated in Fig. l the dam is divided at its downstream face into panels 13 of substantially equal widths by main drainage troughs M which, where convenient are located over construction joints.

As illustrated in Fig. 1, and in greater detail in Figs. 3 and 4, the surface of the concrete is chipped to provide a suitable backing on which to apply the Gunite, the main troughs M are chipped or cut out in the concrete body I l preferably, as above stated along construction joints separating panels l3, and branch troughs l5 draining into the main troughs M are cut or chipped out of the concrete in the various panels. Preferably the branch troughs I5 extend at least half way across a panel and in some instances the high ends of inclined branch troughs at corresponding heights may meet at the middle of the panels.

After their formation, main troughs l5 and branch troughs [5 may be covered respectively by backing plates is and l! of suitable material such as Elastite. Then at the main troughs l4, suitable expansion strips l8 may be placed over the plates l6. Each strip 18 may be of standard construction and consist of a metal strip formed into an inverted U at its center and provided at its edges with flanges extending to substantially two-thirdsthe height of the inverted U. Then a layer of metal mesh I9 is placed over the concrete and. spaced therefrom at a convenient height. The mesh l9 may extend over the flanges at the edges of the expansion strip to the inverted U central portion, where the mesh maybe secured in any suitable manner.

The Gunite may then be applied to the conthe line z -2 of crete until it reaches a suitable thickness. The layer or facing of Gunite is continuous over the branch troughs but is formed over the inverted U portion of each expansion strip with a groove 20. Although it is not necessary, each groove may be filled with any suitable plastic 2|.

It will be evident that with a drainage system such as disclosed, there will be no tendency of the outside coating to crack due to the freezing of water at the rear thereof, or to hydrostatic pressure. The main troughs may drain into a pool at the foot of the dam.

It should be understood that various features may be changed and that certain features may be used without others, without departing from the true spirit and scope of the invention.

What I claim is:

l. A concrete dam built with upright constructional joints dividing the downstream face into panels, water collecting main troughs over said joints, branch troughs collecting water from said panels and discharging it into said main troughs, coverings over said troughs, expansion strips over the coverings of said main troughs, and a Gunite facing covering said downstream face without a break except above the middle portions of the expansion strips where grooves are provided.

2. A dam comprising a concrete body provided at its downstream face with substantially upright main troughs leading down said face at suitable intervals and setting off panels therebetween and with inclined branch troughs collecting water from said panels and discharging it into said main troughs; coverings over all said troughs; expansion devices over the coverings of said main troughs; and a facing of dense cementitious material for said downstream face.

3. The combination of a concrete dam having a system of drainage troughs at the downstream face of the concrete adapted to receive and carry away seepage water from substantially all of said face, and a waterproof covering coat for said downstream face and drainage system, whereby the destructive action of frost either in the main body of the dam or in the covering coat will be eliminated.

4. The combination of a concrete dam having at its downstream face a drainage system comprising troughs to receive and carry away seepage Water from substantially all of its face and coverings over said troughs to form closed ducts, and a waterproof coat of cementitious material covering said downstream. face and drainage system, whereby the destructive action of frost will be eliminated.

BRYAN C. COLLIER. 

